Subject: RE: [Sip] GRUU (was Whats wrong with Supported.

From: "Christian Jansson" <[email-masked]>
Date: Thu, 10 Nov 2005 17:39:42 +0100

Comments below:

>Perhaps you could say something like this:
>
>"The presence of Supported: gruu suggests a high likelihood that the
>Contact is a GRUU, and so a UA using that Contact SHOULD proceed on the
>assumption that it is a GRUU, until it has positive information that it
>is not.  In particular, the UA should not utilize any mechanisms to
work
>around that the Contact is not a GRUU until it has determined that
>utilizing it as a GRUU does not work."
>
>That language:
>
>1) makes all current networks conforming, regardless of "proprietary
>hacks", because no element sends  Supported: gruu yet.
>
>2) when "Supported: gruu" is present, bans proprietary hacks except as
a
>fall-back mechanism.
>
>which seems to me to be a good combination.
>
>Dale

1. Contact URIs should always have been globally routable
2. With GRUU there exists a mechanism to get a contact that fulfills 1.
3. From now on all clients that does what the spec says (1.) must
include Supported: gruu... !!? Otherwise servers that do not follow the
spec break things... but is that not a general rule of broken things? 

Should we also add "Supported: transaction-id" that states that the
transaction id is really unique over space and time, to let the other
side understand that we did not just copy-paste the z9hG4bK into the
branch id without understanding its purpose? Should "Supported:
valid-sip" be added to indicate that we have added all mandatory headers
like to, from, and so on?

My conclusion:
Servers that were broken before and applied hack solutions will not
understand "Supported: gruu" and will continue to apply the hack
solution. Servers that follow the spec and first try the contact as if
it were a GRUU will work regardless of the presence of "Supported:
gruu". Therefore I think the "Supported: gruu" should not be used (apart
from REGISTER).

/ Christian Jansson

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: Paul Kyzivat <[email-masked]>
Date: Thu, 10 Nov 2005 22:07:34 -0500

> gruu". Therefore I think the "Supported: gruu" should not be used (apart

I think there are practical difficulties with this.

In a real deployment you would like the common case to be that things 
work on the first try. If you usually have to try twice then you 
effectively double the amount of signaling your network must support, 
and increase the latency as well.

Following your suggestion, if you deploy a "modern" (gruuful) proxy with 
only gruuless UAs, you would have double the traffic you would have if 
you had the proxy recognize "Supported:gruu".

	Paul